Silver halide emulsion, method of manufacturing the same, and photosensitive material using this emulsion

ABSTRACT

There is disclosed a silver halide photosensitive material having at least one silver halide emulsion layer coated on a support, wherein silver halide grains in the emulsion layer are subjected to reduction sensitization and contain a radical scavenger, prior to the completion of a chemical sensitization. There is also disclosed a silver halide emulsion and a method of manufacturing the same. The said silver halide photosensitive material has a enhanced sensitivity, without causing high fog.

FIELD OF THE INVENTION

The present invention relates to a silver halide photosensitivematerial, and more particularly to a silver halide photosensitivematerial containing reduction-sensitized silver halide grains, whichmaterial has high sensitivity and excellent granularity.

BACKGROUND OF THE INVENTION

In order to obtain high sensitivity, reduction sensitization has beeninvestigated for a long time. Disclosed reduction sensitizers includeTin compounds, in U.S. Pat. No. 2,487,850 by Carrol; polyaminecompounds, in U.S. Pat. No. 2,512,925 by Lowe et al.; and thioureadioxide compounds, in GB Patent No. 789,823 by Fallens et al.Furthermore, physical properties of silver nuclei produced by a varietyof reduction sensitization methods were compared by Collier, asdescribed in Photographic Science and Engineering, 23, p. 113 (1979).She employed several methods using dimethylamine borane, stannouschloride, hydrazine, high pH ripening, and low pAg ripening, for thispurpose. Further, reduction sensitization methods are disclosed in U.S.Pat. Nos. 2,518,698, 3,201,254, 3,411,917, 3,779,777, and 3,930,867. Ameans of reduction sensitization, as well as a selection of reductionsensitizers, is described in JP-B ("JP-B" means examined Japanese patentpublication) Nos. 33572/1982 and 1410/1983. Moreover, a method ofimproving the storage stability of reduction-sensitized emulsions isdisclosed in JP-A ("JP-A" means unexamined published Japanese patentapplication) Nos. 82831/1982 and 178445/1985. Further, Takada et al.disclose a method of preparing an emulsion reduction-sensitized withthiosulfonic acid, in JP-A No. 191938/1990. Though many investigationswere tried as mentioned above, these reduction sensitization methodswere not adequate for providing sufficiently high sensitivity, ascompared to hydrogen sensitization, wherein a photosensitive material issubjected to hydrogen gas processing. This is reported by Moisar et al.in the Journal of Imaging Science, vol. 29, p. 233 (1985).

On the other hand, JP-A No. 162546/1984 discloses that a hydroxyl aminecompound improves latent image intensification. However, this method didnot give high sensitivity to a silver halide emulsion.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a silver halidephotosensitive material that has enhanced sensitivity without increasingfog.

Other and further objects, features, and advantages of the inventionwill appear more fully from the following description.

DETAILED DESCRIPTION OF THE INVENTION

As a result of intensive investigation, the present inventors have foundthat the above-mentioned object of this invention can be achieved by:

(1) A silver halide emulsion, subjected to both reduction sensitizationand gold chalcogen sensitization (an ordinary gold sensitization andchalcogen sensitization may be performed), and containing at least aradical scavenger;

(2) A method of manufacturing a silver halide emulsion, which comprisessteps of subjecting the silver halide emulsion to reductionsensitization, and then adding thereto at least a radical scavenger,prior to completion of gold chalcogen sensitization;

(3) A silver halide photosensitive material that comprises a supporthaving thereon at least one layer containing a silver halide emulsion,wherein the silver halide emulsion is manufactured by steps ofsubjecting the silver halide emulsion to reduction sensitization, andthen adding thereto at least a radical scavenger, prior to thecompletion of gold chalcogen sensitization;

(4) A silver halide photosensitive material having at least one silverhalide emulsion layer coated on a support, wherein silver halide grainsin the emulsion layer are subjected to reduction sensitization, andwherein the silver halide photosensitive material contains a radicalscavenger represented by general formula (A) as set forth below, priorto the completion of a chemical sensitization: ##STR1## wherein R_(a1)represents an alkyl group, an alkenyl group, an aryl group, aheterocyclic group, an acyl group, a sulfonyl group, a sulfinyl group, acarbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, or anaryloxycarbonyl group; R_(a2) is a hydrogen atom or a group representedby R_(a1), with the proviso that when R_(a1) is an alkyl group, analkenyl group, or an aryl group, R_(a2) is a heterocyclic group, an acylgroup, a sulfonyl group, a sulfinyl group, a carbamoyl group, asulfamoyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group;and R_(a1) and R_(a2) may combine together to form a 5- to 7-memberedring;

(5) The silver halide photosensitive material as described in (4),wherein said silver halide grains, subjected to the reductionsensitization and containing the radical scavenger represented bygeneral formula (A), in said emulsion layer are tabular silver halidegrains having an aspect ratio of not less than 3, and having dislocationlines, in an amount of at least 60% of the total projected area of thesegrains; and

(6) The silver halide color photosensitive material as described in (3),(4), or (5), containing at least a color coupler.

The reduction sensitization used in the present invention is explainedbelow.

The production steps of the silver halide emulsion are classified into agrain formation step, a desalting step, a chemical sensitization step,etc. The grain formation step is classified into core grain formation,ripening, growth, etc. These steps may be variably preformed; that is,the step order may be changed or some steps may be repeated. The term"to be subjected to reduction sensitization during the production of thesilver halide emulsion" means that basically the reduction sensitizationcan be performed in any step. In other words, reduction sensitizationmay be carried out at any time, including core grain formation (i.e.,the initial stage of the grain formation), physical ripening, growth,the period prior to a chemical sensitization other than the reductionsensitization, or after the completion of the chemical sensitization.The chemical sensitization herein referred to means a chemicalsensitization except for the reduction sensitization. When a chemicalsensitization is performed in combination with the gold sensitization,it is preferable to perform the reduction sensitization prior to thechemical sensitization, so that undesirable fog may not be formed. It ismost preferable to carry out the reduction sensitization during growthof the silver halide grains. The words "during growth" herein referredto mean that the reduction sensitization is being carried out while thesilver halide grains are growing by means of physical ripening or theaddition of a water-soluble silver salt and a water-soluble alkalihalide. In addition, the words also mean that the reductionsensitization is carried out in a condition wherein growth of the silverhalide grains is temporarily stopped, and then the growth is resumed.

As the reduction sensitization of the present invention, any one of thefollowing can be used: a method wherein a known reduction sensitizingagent is added to a silver halide emulsion; a method called silverripening, wherein growing or ripening is carried out in an atmospherehaving a pAg as low as 1 to 7; and a method called high-pH ripening,wherein growing or ripening is carried out in an atmosphere having a pHas high as 8 to 11. Two or more of these methods can be used incombination.

The method wherein a reduction sensitizing agent is added is apreferable method because the level of the reduction sensitization canbe adjusted subtly.

As the reduction sensitizing agent, stannous salts, amines andpolyamines, hydrazine derivatives, formamidine sulfinic acid, silanecompounds, and borane compounds are known. For the reductionsensitization of the present invention, these known reductionsensitizing agents can be chosen to be used, and two or more of thesecompounds can be used in combination. As the reduction sensitizingagent, stannous chloride, thiourea dioxide, and dimethylamineborane arepreferable compounds. Although the amount of the reduction sensitizingagent to be added is dependent on the production conditions of theemulsion, suitable amounts are in the range of 10⁻⁷ to 10⁻³ mol per molof the silver halide.

As the reduction sensitizing agent of the present invention, ascorbicacid and its derivatives can also be used.

As specific examples of ascorbic acid and its derivatives (hereinafterreferred to as "ascorbic acid compound"), the following can bementioned:

(AA-1) L-ascorbic acid

(AA-2) Sodium L-ascorbate

(AA-3) Potassium L-ascorbate

(AA-4) DL-ascorbic acid

(AA-5) Sodium D-ascorbate

(AA-6) L-ascorbic acid-6-acetate

(AA-7) L-ascorbic acid-6-palmitate

(AA-8) L-ascorbic acid-6-benzoate

(AA-9) L-ascorbic acid-5,6-diacetate

(AA-10) L-ascorbic acid-5,6-O-isopropylidene

(AA-11) D-ascorbic acid

Preferably the ascorbic acid compound used in the present invention isused in a larger amount than the conventional amount in which areduction sensitizer is preferably used. It is described in, forexample, JP-B No. 33572/1982, that the amount of the reductionsensitizer is usually not larger than 0.75×10⁻² milliequivalents per 1 gof silver ion (8×10⁻⁴ mol per 1 mol of AgX), and the amount of 0.1 to 10mg per 1 kg of silver nitrate (10⁻⁷ to 10⁻⁵ mol of ascorbic acid per 1mol of AgX) is effective in many occasions (the conversion values werecalculated by the present inventor). U.S. Pat. No. 2,487,850 describesthat the addition amount of a tin compound as a reduction sensitizer is1×10⁻⁷ to 44×10⁻⁶ mol. Further, JP-A No. 179835/1982 describes that itis suitable to use thiourea dioxide in an amount of about 0.01 mg toabout 2 mg per 1 mol of silver halide, and stannous chloride in anamount of about 0.01 mg to about 3 mg per 1 mol of silver halide. Apreferable addition amount of the ascorbic acid compound used in thepresent invention varies depending on such factors as the grain size ofthe silver halide emulsion, the halogen composition thereof, and each ofthe temperature, pH, and pAg used for the production of the silverhalide emulsion. However, generally a preferable addition amount may beselected from a range of 5×10⁻⁵ to 1×10⁻¹ mol per 1 mol of silverhalide, more preferably from 5×10⁻⁴ mol to 1×10⁻² mol, and mostpreferably from 1×10⁻³ mol to 1×10⁻² mol.

The reduction sensitizing agent is dissolved in a solvent, such aswater, alcohols, glycols, ketones, esters, and amides; and it is addedduring the formation of the grains, before the chemical sensitization,or after the chemical sensitization. The reduction sensitizing agent maybe added in any step of producing the emulsion, and particularlypreferably it is added during the growth of the grains. Although thereduction sensitizing agent may previously be added into a reactionvessel, preferably the reduction sensitizing agent is added at asuitable time during the growth of the grains. It is also possible thatthe reduction sensitizing agent may be previously added to an aqueoussolution of a water-soluble silver salt or a water-soluble alkali halidesolution, and then these aqueous solutions are used to precipitatesilver halide grains. Also, preferably a solution of the reductionsensitizing agent is added in portions or continuously during the growthof the grains over a long period of time.

The radical scavenger used in the present invention is a compound thatis able to make galvinoxyl substantially colorless (decrease theabsorption efficient of galvinoxyl at 430 nm). This is determined by thefollowing steps: (1) mixing an ethanol solution containing 0.05 mmoldm⁻³ of galvinoxyl and an ethanol solution containing 2.5 mmol dm⁻³ of atest compound at 25° C. according to a stopped flow method, and then (2)measuring the change of absorption efficient at 430 nm over a certainperiod of time. When the test compound does not fully dissolve at thegiven concentration, a measurement of the absorption efficient may beperformed at a lower concentration.

The color diminishing velocity constant of galvinoxyl determined by theabove method is preferably not less than 0.01 mmol⁻¹ s⁻¹ dm³, and morepreferably not less than 0.1 mmol⁻¹ s⁻¹ dm³.

A method of determining a radical scavenging velocity using galvinoxylis described in Microchemical Journal, 31, pp. 18 to 21 (1985), and thestopped flow method is described in, for example, Bunko-kenkyu(Spectroscopic study), 19, No. 6 (1970) p. 321.

It is more preferable to use a compound represented by general formula(A) as a radical scavenger in the present invention. The compoundrepresented by general formula (A) is explained below in detail.##STR2##

In general formula (A), R_(a1) represents an alkyl group preferablyhaving 1 to 36 carbon atoms, and more preferably 1 to 26, such asmethyl, ethyl, i-propyl, cyclopropyl, butyl, isobutyl, cyclohexyl,t-octyl, decyl, dodecyl, hexadecyl, and benzyl; an alkenyl grouppreferably having 2 to 36 carbon atoms, and more preferably 2 to 26,such as allyl, 2-butenyl, isopropenyl, oleyl, and vinyl; an aryl grouppreferably having 6 to 40 carbon atoms, and more preferably 6 to 30,such as phenyl and naphthyl; a heterocyclic group that is a groupcapable of forming a 5- to 7-membered hetero ring, which ring containsat least one of ring-forming atoms consisting of a nitrogen atom, asulfur atom, an oxygen atom, and a phosphorus atom (preferably anitrogen atom-containing heterocyclic group, more preferably aheterocyclic group containing 1 to 4 nitrogen atoms, and most preferablya 5- to 6-membered heterocyclic group containing 1 to 3 nitrogen atoms),such as 1,3,5-triazine-2-yl, 1,2,4-triazine-3-yl, pyridine-2-yl,pyrazinyl, pyrimidinyl, purinyl, quinolyl, imidazolyl,1,2,4-triazole-3-yl, benzimidazole-2-yl, thienyl, furyl, imidazolidinyl,pyrrolinyl, tetrahydrofuranyl, and morpholinyl; an acyl group, such asacetyl, benzoyl, pyvaloyl, α-(2,4-di-tert-amylphenoxy)butylyl,myristoyl, stearoyl, naphthoyl, m-pentadecylbenzoyl, and isonicotinoyl;a sulfonyl group (preferably alkane or aryl sulfonyl groups), such asmethanesulfonyl, octane sulfonyl, benzenesulfonyl, and toluensulfonyl; asulfinyl group (preferably alkane or aryl sulfinyl groups), such asmethanesulfonyl and benzenesulfinyl; a carbamoyl group, such asN-ethylcarbamoyl, N-phenylcarbamoyl, N,N-dimethylcarbamoyl, andN-butyl-N-phenylcarbamoyl; a sulfamoyl group, such as N-methylsulfamoyl,N,N-diethylsulfamoyl, N-phenylsulfamoyl; N-cyclohexyl-N-phenylsulfanoyl,and N-ethyl-N-dodecylsulfamoyl; an alkoxycarbonyl group, such asmethoxycarbonyl, cyclohexyloxycarbonyl, benzyloxycarbonyl,isoamyloxycarbonyl, and hexadecyloxycarbonyl; or an aryloxycarbonylgroup, such as phenoxycarbonyl and naphthoxycarbonyl. R_(a2) representsa hydrogen atom or groups represented by R_(a1). R_(a1) and R_(a2) maybe combined together to form a 5- to 7-membered ring, such as asuccinimide ring, a phthalimide ring, a triazole ring, a urazol ring, ahydantoin ring, and a 2-oxo-4-oxazolidinone ring.

Groups each represented by R_(a1) and R_(a2) in general formula (A) maybe further substituted with substituents. Examples of these substituentsinclude an alkyl group, an alkenyl group, an aryl group, a heterocyclicgroup, a hydroxyl group, an alkoxy group, an aryloxy group, an alkylthiogroup, an arylthio group, an amino group, an acylamino group, asulfonamide group, an alkylamino group, an arylamino group, a carbamoylgroup, a sulfamoyl group, a sulfo group, a carboxyl group, a halogenatom, a cyano group, a nitro group, a sulfonyl group, an acyl group, analkoxycarbonyl group, an aryloxycarbonyl group, an acyloxy group, and ahydroxyamino group.

Of compounds represented by general formula (A), preferred ones arethose wherein R_(a1) is a heterocyclic group, and more preferably aheterocyclic aromatic group that includes a heterocyclic ring that isable to form a heterocyclic aromatic ring in form, as one of the ring'sequilibrium structures. The term "heterocyclic aromatic group" ishereinafter used in this meaning. More preferable compounds arerepresented by the following general formula (A-I): ##STR3## whereinR'_(a2) represents a hydrogen atom, an alkyl group, an alkenyl group, oran aryl group, and Z represents a heterocyclic aromatic group.

Of compounds represented by general formula (A-1), preferred ones arethose wherein R'_(a2) represents a hydrogen atom or an alkyl group, oralternatively Z represents a heterocyclic aromatic group containing acarbon atom and a nitrogen atom as a ring-forming atom, and morepreferably Z is non-metallic atoms necessary to complete a 5- to7-membered heteroring containing 1 to 4 nitrogen atoms.

The most preferable compounds are represented by the following generalformula (A-II): ##STR4## wherein R'_(a2) has the same meanings asR'_(a2) in general formula (A-I), and R_(a3) and R_(a4), which are sameor different, each represent a hydrogen atom or a substituent.

Of compounds represented by general formula (A-II), preferred ones areparticularly those wherein R_(a3) and R_(a4) each represent ahydroxyamino group, a hydroxyl group, an amino group, an alkylaminogroup, an arylamino group, an alkoxy group, an aryloxy group, analkylthio group, an arylthio group, an alkyl group, or an aryl group.

Specific examples of compounds represented by general formula (A)according to the present invention are illustrated below, but they arenot intended to restrict the scope of the present invention. ##STR5##

These compounds according to the present invention can be easilysynthesized by the methods described in, for example, J. Org. Chem., 27,4054 ('62); J. Amer. Chem. Soc., 73, 2981 ('51); and JP-B No.10692/1974, or in a similar manner.

The color-diminishing velocity constants of galvinoxyl, which weredetermined using several radical scavengers, are shown in Table 1.

                  TABLE 1    ______________________________________                 Color-deminishing                 volocity constant    Compound     (mmol.sup.-1 S.sup.-1 dm.sup.3)    ______________________________________    A-3          0.8    A-4          0.3    A-9          0.9    ______________________________________

In the present invention, a radical scavenger may be added as asolution, in which case the scavenger is dissolved in a water-solubleliquid, such as water, methanol, and ethanol; or alternatively thescavenger may be added as an emulsified dispersion. When the scavengeris dissolved in water, it may be dissolved at a high or low pH dependingon its better solubility, to make an aqueous solution, and then the thusobtained solution is added.

In the present invention, two or more kinds of radical scavengers may beused in combination.

In the present invention, the radical scavenger may be added at any timefrom the beginning of the grain formation but prior to the completion ofa chemical sensitization, but it is preferable to add the scavengerafter the completion of a reduction sensitization, and more preferablybefore the beginning of the chemical sensitization. Further, the pHvalue at which the radical scavenger is added is preferably 7 or less,and more preferably 6 or less.

In the present invention, the term "before the beginning of the chemicalsensitization" herein referred to means the time before a chalcogensensitizer or a gold sensitizer is added, and the term "the completionof a chemical sensitization" means a point of time when the temperatureis reduced to finish the chemical sensitization.

In the present invention, the addition amount of the radical scavengeris preferably from 1×10⁻⁵ to 1×10⁻² mol per 1 mol of Ag, and morepreferably from 1×10⁻⁴ to 5×10⁻³ mol per 1 mol of Ag.

Multiple silver halide emulsions are usually employed in a multilayersilver halide photosensitive material, and when some of the emulsionsare those of the present invention, the addition amount of a radicalscavenger based on the silver halide emulsion of the present inventionis substantially reduced, because the radical scavenger diffuses in thephotosensitive material. For this reason, the radical scavenger may befurther added at the coating.

A silver halide photosensitive material of the present inventionpreferably further contains at least one compound selected from thecompounds represented by general formula (B), (C), or (D):

general formula (B) R³ --SO₂ S--M

general formula (C) R³ --SO₂ S--R⁴

general formula (D) R³ --SO₂ S--Lm--SSO₂ --R⁵

wherein R³, R⁴, and R⁵ which are same or different, each represent analiphatic group, an aromatic group, or a heterocyclic group; Lrepresents a divalent group; M represents a cation; and m represents aninteger of 0 or 1.

The compounds of general formulae (B), (C), and (D) are furtherexplained below in detail.

Where R³, R⁴, and R⁵ are each an aliphatic group, preferred examplesthereof are an alkyl group having 1 to 22 carbon atoms, an alkenyl grouphaving 2 to 22 carbon atoms and an alkynyl group, each of which may havea substituent. Specific examples of the alkyl group include methyl,ethyl, propyl, butyl, pentyl, hexyl, octyl, 2-ethylhexyl, decyl,dodecyl, hexadecyl, octadecyl, cyclohexyl, isopropyl, and t-butyl.

Specific examples of the alkenyl group are allyl and butenyl.

Specific examples of the alkynyl group are propargyl and butynyl.

The aromatic group of R³, R⁴, and R⁵ preferably has 6 to 20 carbonatoms, and it includes a phenyl group and a naphthyl group, each ofwhich may be substituted.

Examples of the heterocyclic group of R³, R⁴, and R⁵ are those composedof a 3- to 15-membered ring containing at least one element selectedfrom nitrogen, oxygen, sulfur, selenium, and tellurium, such as apyrrolidine ring, a peperidine ring, a pyridine ring, a tetrahydrofuranring, a thiophene ring, an oxazole ring, a thiazole ring, an imidazolering, a benzothiazole ring, a benzoxazole ring, a benzimidazole ring, aselenazole ring, a benzselenazole ring, a tetrazole ring, a triazolering, a benzotriazole ring, a tetrazole ring, an oxadiazole ring, and athiadiazole ring.

Examples of the substituent for R³, R⁴, and R⁵ are an alkyl group (e.g.,methyl, ethyl, and hexyl), an alkoxy group (e.g., methoxy, ethoxy, andoctyloxy), an aryl group (e.g., phenyl, naphthyl, and tolyl), a hydroxylgroup, a halogen atom (e.g., fluorine, chlorine, bromine, and iodine),an aryloxy group (e.g., phenoxy), an alkylthio group (e.g., methylthioand butylthio), an arylthio group (e.g., phenylthio), an acyl group(e.g., acetyl, propionyl, butyryl and valeryl), a sulfonyl group (e.g.,methylsulfonyl and phenylsulfonyl), an acylamino group (e.g.,acetylamino and benzamino), a sulfonyl amino group (e.g.,methanesulfonylamino and benzenesulfonylamino), an acyloxy group (e.g.,acetoxy and benzoxy), a carboxyl group, a cyano group, a sulfo group, anamino group, etc.

L is preferably a divalent aliphatic group or a divalent aromatic group.Specific examples of the divalent aliphatic group of L include .parenopen-st.CH₂ .paren close-st._(n) (n=1 to 12), --CH₂ --CH═CH--CH₂ --,--CH₂ --C.tbd.C--CH₂ --, ##STR6## and a xylylene group. Specificexamples of the divalent aromatic group of L include phenylene andnaphthylene.

These divalent aliphatic or aromatic groups may be further substitutedwith such a substituent as mentioned hereinbefore.

M is preferably a metal ion or an organic cation. Examples of the metalion include a lithium ion, a sodium ion, and a potassium ion. Examplesof the organic cation include an ammonium ion (e.g., ammonium,tetramethylammonium, and tetrabutylammonium), and phosphonium ion (e.g.,tetraphenyl phosphonium), and a quanidine group.

Specific examples of the compounds represented by general formula (B),(C), or (D) are illustrated below, but they are not intended to restrictthe scope of the present invention. ##STR7##

The compounds of general formula (B) can be easily synthesized by themethods as described in JP-A No. 1019/1979 and GB Patent No. 972,211.

It is preferable to add the compound of general formula (B), (C), or (D)in an amount of 10⁻⁷ to 10⁻¹ mol, more preferably 10⁻⁶ to 10⁻² mol, mostpreferably 10⁻⁵ to 10⁻³ mol, per 1 mol of silver halide, respectively.

In order to add the compound of general formula (B), (C), or (D) duringproduction steps of the photographic emulsion, use can be made of aconventional method that is ordinarily used to incorporate additivesinto a photographic emulsion. For example, a water-soluble compound canbe added as an aqueous solution having a suitable concentration. On theother hand, a water-insoluble or sparingly water-soluble compound can bedissolved in a suitable organic solvent, which has miscibility withwater, e.g., a solvent that is selected from alcohols, glycols, ketones,esters, and amides, and which yet does not give any harm to photographicproperties; and then this combination may be added as a solution.

The compound of general formula (B), (C), or (D) may be added to asilver halide emulsion at any stage of the production thereof, i.e.,during grain formation or before or after a chemical sensitization. Itis preferable to add the compound at any time before or during reductionsensitization. It is particularly preferable to add the compound duringgrain formation.

The compound may be previously added to a reaction vessel. However, itis preferred to add the compound at a suitable stage of the grainformation, rather than the above-mentioned method. Further, silverhalide grains may be formed using an aqueous solution of a water-solublesilver salt and an aqueous solution of a water-soluble alkali halide, atleast one of which solutions previously contains the compound of generalformula (B), (C), or (D). Further, it is preferable to add a solutioncontaining the compound of general formula (B), (C), or (D) in a dividedmanner or continuously for a long period of time, during grainformation.

Of the compounds represented by general formulae (B), (C), and (D), mostpreferred compounds for the present invention are one of general formula(B).

An emulsion of the present invention preferably contains tabular silverhalide grains having an aspect ratio of not less than 3, and morepreferably 3 or more, but less than 8. The term "tabular grains" hereinreferred to is a general term of the grains having one twin face, or twoor more parallel twin faces. The twin face means the (111) face whenions on all of the lattice points at both sides of a (111) face havemirror-image relations. These tabular grains, when viewed in a directionperpendicular to the major faces, are triangular, hexangular, orcircular (rounded triangular or hexangular in shape). The triangulargrains, the hexangular grains, and the circular grains each haveparallel outer surfaces having a triangular, hexangular, and circularshape, respectively.

The aspect ratio of the tabular grains according to the presentinvention means the value of the grain diameter divided by the thicknessof the grain with respect to each tabular grains having a 0.1 μm orlarger diameter. The thickness of a grain can be easily determined bythe following steps: (i) vaporizing a metal from an oblique direction ofthe grain with a latex for reference, (ii) measuring the length of theshadow on an electron micrograph, and then (iii) evaluating the lengthof the shadow of the metal with reference to the length of the shadow ofthe latex.

The grain diameter herein referred to means the diameter of a circlehaving an area equal to the projected area of the parallel outersurfaces of the grain.

The projected area of the grain is obtained by measuring an area on anelectron micrograph, and then correcting a photographing magnification.

The diameter of the tabular grains is preferably 0.15 to 5.0 μm.Preferably the thickness of such tabular grains is 0.05 to 1.0 μm.

The average aspect ratio is determined as an arithmetic mean of eachaspect ratio for at least 100 grains of silver halide grains. Further,the average aspect ratio can be determined as a ratio of the averagediameter to the average thickness of the grains.

The emulsion of the present invention contains tabular silver halidegrains having an aspect ratio of 3 or over, and preferably an averageaspect ratio of 3 or over but less than 8. Preferably such tabularsilver halide grains occupy 60% or more of all the projected areas ofthe emulsion.

Preferably the ratio of the tabular grains is such that those amount to60% or more, and particularly preferably 80% or more, of all theprojected areas.

In some cases, monodisperse tabular grains are used to obtain morepreferable results. The structure of monodisperse tabular grains and themethod for producing them follow the description, for example, of JP-ANo. 151618/1988. The shape thereof can be described briefly as follows:70% or more of all the projected areas of silver halide grains havehexagonal shapes wherein the ratio of the length of the longest side tothe length of the shortest side is 2 or less, and are taken up bytabular silver halide having two parallel outer surfaces. Further, withrespect to the hexagonal tabular silver halide grains, the deviationcoefficient (the value obtained by dividing the scatter (standarddeviation) of the grain sizes in terms of the diameter of the projectedarea with the shape of the grain assumed to be as a circle by theaverage grain size) of the grain size distribution of the hexagonaltabular silver halide grains is 20% or less, which shows monodispersionproperties.

Further, the grains in the emulsion of the present invention preferablyhave dislocation lines. Dislocations of the tabular grains can beobserved by a direct observation method using a low-temperaturetransmission electron microscope, as described, for example, in J. F.Hamilton, Phot. Sci. Eng., 11, 57 (1967); and T. Shiozawa, J. Soc. Phot.Sci. Japan, 35, 213 (1972). That is silver halide grains, which havebeen taken out from the emulsion with care so that pressure that wouldcause dislocations in the grains would not be applied, are placed on amesh for electron microscope observation and are observed by thetransmission method with the sample cooled to prevent damage (e.g.,printout) due to an electron ray. In this case, the thicker the grainsare, the less the electron ray is transmitted, and therefore if ahigh-voltage (200 kV or higher for grains having a thickness of 0.25 μm)electron microscope is used, a more clear observation can be made. Fromthe photograph of the grains taken by using the method as describedabove, the positions and the number of dislocations of each grain viewedperpendicularly to the principal plane can be determined.

The number of dislocation lines is 10 or more, and more preferably 20 ormore, per grain on average. When the dislocation lines exist in acrowded condition, or are viewed as being crossed with each other, it issometimes difficult to exactly count the number of dislocation lines pergrain. However, it is possible to count them with such accuracy asidentifying about 10, 20, or 30 lines, even in these cases, which can beclearly distinguished from there being only several dislocation linespresent. The average number of dislocation lines per grain is determinedby counting the number of dislocation lines with respect to 100 grainsor more, and then averaging them in number.

The dislocation lines can be introduced into, for example, an outersurface or its vicinity of a tabular grain. In this case, thedislocations are almost perpendicular to the outer surface, anddislocation lines are generated in a direction from a position away fromthe center of the tabular grain by a distance that is ×% of a lengthbetween the center and an edge, to the edge. A value of × is preferably10 or more, but less than 100, more preferably 30 or more, but less than99, and most preferably 50 or more, but less than 98. In this case, ashape that is obtained by connecting positions at which dislocationsstart is close to a similar figure of the tabular grain, but is notalways a completely similar figure, i.e., sometimes the shape isdistorted. A dislocation of this type is not viewed in a center regionof the grain. The direction of dislocation lines is crystallographicallyabout the direction of (211), but sometimes the dislocation lines extendin a zigzag manner, or cross each other.

Further, the tabular grain may have the dislocation lines almostuniformly at all through the outer surface or at a localized region onthe outer surface. Taking hexangular tabular silver halide grains as anexample, the dislocation lines may be limited to only a vicinity of 6apices, or to only a vicinity of 1 apex among the 6 apices. On thecontrary, the dislocation lines can be limited to only the sides (edges)excluding a vicinity of the 6 apices.

Further, the dislocation lines may be formed over the region including acenter of two parallel major planes of the tabular grain. When thedislocation lines are formed all over the region of the major planes, adirection of the dislocation lines, when viewed from the directionperpendicular to the major plane, is usually crystallographically almostthe direction of (211), but sometimes the direction is of (110) or atrandom. Furthermore, each length of the dislocation lines is alsorandom. Therefore some dislocation lines are observed as a short line onthe major plane and other dislocation lines are observed as a long lineextending to the side (outer surface). Some dislocation lines arestraight, but many others extend in a zigzag manner. Further, in manycases they are crossed.

The position of dislocations may be limited to on the outer surface, themajor plane, or a localized region as mentioned above, or thedislocations may be formed at a combination thereof. That is to say, thedislocations may exist simultaneously on both the outer surface and themajor plane.

In order to introduce dislocation lines on the outer surface of thetabular grain, specific high-silver iodide layers (phases) can be formedin an internal portion of the tabular grains. The high-silver iodidelayer herein referred to includes discontinuous high-silver iodideregions. Specifically, such tabular grains can be obtained by the stepsof preparing substrate grains, and then forming a high-silver iodidelayer on the substrate grains, followed by covering them with a layerhaving an iodide content lower than that of the high-silver iodidelayer. The silver iodide content of the tabular substrate grains islower than that of the high-silver iodide layer, and it is preferablyfrom 0 to 20 mol %, more preferably from 0 to 15 mol %.

The "high-silver iodide layer in an internal portion of the grain"herein referred to means a silver halide solid solution containingsilver iodide. Preferred silver halides are silver iodide, silveriodobromide, and silver chloroiodobromide, and more preferably silveriodide and silver iodobromide (silver iodide content: 10 to 40 mol %).In order to form a high-silver iodide layer in an internal selectiveposition of the grain (hereinafter referred to as an internalhigh-silver iodide layer), i.e., an edge or a corner of the substrategrains, such localization can be controlled by conditions for formingthe substrate grains and the internal high-silver iodide layers. Of theconditions for forming the substrate grains, there can be recited pAg(the cologarithm of silver ion density), a silver halide solvent (apresence or absence, a kind, and an amount thereof), and temperature asan important factor. It is possible to selectively form internalhigh-silver iodide layers at the vicinity of corners of the substrategrains, by adjusting pAg to 8.5 or less, and more preferably to 8 orless, when the substrate grains are growing. On the other hand, internalhigh-silver iodide layers can be formed selectively on the edges of thesubstrate grains, by adjusting pAg to more than 8.5, and more preferably9 or more, when the substrate grains are growing. The threshold value ofthe pAg varies up and down depending on temperature; and the presence orabsence, the kind, and the amount of the silver halide solvent. Forexample, when a thiocyanate compound is used as a silver halide solvent,the threshold of the pAg inclines upward. The pAg at the terminal stageof the growth is particularly important as a pAg when the substrategrains are growing. On the other hand, even when the pAg at the step ofthe growth is out of the above given value, the selective location ofthe internal high-silver iodide layer can be controlled by adjusting thepAg to the above given value after the substrate grains have grown,followed by ripening. In this case, ammonia, amine compounds, andthiocyanate salts are useful as a silver halide solvent. The internalhigh-silver iodide layer can be formed by a so-called conversion method.In this method, during a grain formation process, halide ions having alower solubility of salt forming silver ion than that of silver halidethat forms a grain (or a portion close to the surface of grain) at thistime, are added. In this invention, an amount of the halide ions havinga lower silver salt solubility to be added is preferably larger than avalue (associated with a halide composition) with respect to a surfacearea of the grain at this time. For example, during grain formation, KIis preferably added in an amount larger than a certain value withrespect to a surface area of an AgBr grain at this time. Morespecifically, iodide salt is preferably added in an amount of 8.2×10⁻⁵mol/m² or more.

A more preferable method of producing an internal high-silver iodidelayer is to simultaneously add a silver salt aqueous solution and anaqueous solution of a halide salt containing an iodide salt.

For instance, a silver nitrate aqueous solution is added simultaneouslywith a potassium iodide aqueous solution according to a double jetmethod. In this method, there may be a difference in addition-startingtime and/or addition-terminating time between the potassium iodideaqueous solution and the silver nitrate aqueous solution. The molarratio of the silver nitrate aqueous solution to be added to thepotassium iodide aqueous solution is preferably not less than 0.1, morepreferably not less than 0.5, and most preferably not less than 1. Thetotal addition molar amount of the silver nitrate aqueous solution maybe a region wherein silver is excessive compared to an amount of ahalogen ion in the system and an iodine ion to be added. Preferably thepAg value at the time when an aqueous solution of a halide containing aniodine ion is added with a silver salt aqueous solution according to adouble jet method, declines with the addition period involved accordingto the double jet method. The pAg value at the time when an additionstarts is preferably from 6.5 to 13, and more preferably from 7.0 to 11.On the other hand, the pAg value when the addition is terminated is mostpreferably from 6.5 to 10.0.

When the above-mentioned methods are preformed, the solubility of thesilver halide to be mixed is preferably as low as possible. Accordingly,the temperature of the mixture at the time when a high-silver iodidelayer is formed is preferably from 30° C. to 70° C., and more preferablyfrom 30° C. to 50° C.

Most preferably, the internal high-silver iodide layer can be formed byadding a fine-grain silver iodide (i.e., fine particles of silveriodide; the term "fine grain" is hereinafter used in the same meaning),or a fine-grain silver iodobromide, or a fine-grain silver chloroiodido,or a fine-grain silver chloroiodobromide. The addition of fine-grainsilver iodide is particularly preferred. The grain size of these finegrains is usually from 0.01 μm to 0.1 μm. However, it is possible to usefine grains having a grain size of less than 0.01 μm or more than 0.1μm. These fine-grain silver halides can be prepared with reference tomethods described in Japanese patent application Nos. 7851/1988,195778/1988, 7852/1988, 7853/1988, 194861/1988, and 194862/1988. Aninternal high-silver iodide layer can be formed by adding thesefine-grain silver halides, and then aging. The above-mentioned silverhalide solvent may be used in order to dissolve the fine grains byaging. All of the fine grains that are added are not necessarilyinstantly dissolved and consumed; rather it is adequate if they arecompletely dissolved and consumed by the time the final grains have beenformed.

The silver iodide content of an outer layer with which an internalhigh-silver iodide layer is covered, should be lower than that of theinternal high-silver iodide layer, preferably such silver iodide contentis from 0 to 30 mol %, more preferably from 0 to 20 mol %, and mostpreferably from 0 to 10 mol %. The location of internal high-silveriodide layers, when measured from a center of a hexangle, etc., formedby a projection of the grain, preferably exists in a range of 5 mol % ormore, but less than 100 mol %; more preferably 20 mol % or more, butless than 95 mol %; and most preferably 50 mol % or more, but less than90 mol %, with respect to the silver amount of the entire silver halidegrain. The silver amount of silver halide that constitutes the internalhigh-silver iodide layer is preferably 50 mol % or less, and morepreferably 20 mol % or less, of the silver amount of the entire silverhalide grain. The above-mentioned amounts with respect to the internalhigh-silver iodide layer are based on a recipe for the production ofsilver halide emulsions, rather than on the values observed by ameasurement according to several analytical methods of a halidecomposition of the final grains. This is because the internalhigh-silver iodide layer in the final grains often vanishes during arecrystallization step or the like. The all mentioning to the aboverefers to the production method.

Accordingly, the internal silver iodide layer formed to introducedislocation lines into the final grains is often difficult to observe asa definite layer, even though the dislocation lines in the final grainscan be easily observed according to the above-mentioned methods. Forexample, an entire outer surface region of the tabular grains issometimes observed as a high-silver iodide layer. The halogencomposition of the tabular grains can be identified by a combination of,for example, X-ray diffraction, an EPMA (also called an XMA) method (inwhich silver halide grains are scanned by an electron beam to detect asilver halide composition), and an ESCA (also called an XPS) method (inwhich X rays are radiated to perform spectroscopy for photoelectronsemitted from the grain surface).

The temperature and the pAg to be used for the formation of externallayers covering internal high-silver iodide layers are not limited inparticular, but a preferable temperature is from 30° C. to 80° C., andmost preferably from 35° C. to 70° C. A preferable pAg is from 6.5 to11.5. Use of the above-mentioned silver halide solvent is sometimespreferred. The most preferred silver halide solvent is a thiocyanatesalt.

Dislocation lines can be introduced into major planes of the tabulargrains by the following steps: substrate grains are prepared; a silverhalochloride is deposited on the major planes of the grains; the silverhalochloride is subjected to a halogen conversion, to form high-silverbromide or high-silver iodide layers, and then these layers are coveredwith shells. As such the silver halochloride, can be mentioned silverchloride, silver chlorobromide, or silver chlorodiodobromide, eachhaving a silver chloride content of not less than 10 mol %, andpreferably not less than 60 mol %. A deposition of the silverhalochloride on the major planes of the substrate grains can beperformed by adding a silver nitrate aqueous solution and an aqueoussolution of a suitable alkali metal salt (e.g., potassium chloride),separately or simultaneously, or alternatively by adding the thusobtained silver salt emulsion, and then followed by ripening. Thedeposition of the silver halochloride can be performed in any pAgregion, but the most preferred region is from 5.0 to 9.5. According tothese methods, tabular grains grow mainly in a width direction thereof.The amount of silver halochloride layers is preferably from 1 mol % to80 mol %, and more preferably from 2 mol % to 60 mol %, in terms of thesilver content to the entire substrate grain. Dislocation lines can beprovided on major planes of the tabular grains, by subjecting the silverhalochloride layers to a halogen conversion with a halide aqueoussolution that is able to form a silver salt having a lower solubilitythan that of the silver halochloride. For example, the silverhalochloride layers are subjected to a halogen conversion with a KIaqueous solution, and then shells are grown on the layers, whereby finalgrains can be obtained. The halogen conversion of these silverhalochloride layers herein referred to does not mean that the entiresilver halochloride is converted to a silver salt having a lowersolubility than that of the silver halochloride, but preferably not lessthan 5%, more preferably not less than 10%, and most preferably not lessthan 20%, of the silver halochloride is converted to a silver salthaving a lower solubility. Dislocation lines can be provided at a localportion of major planes by controlling the structure of the halogencomposition of substrate grains in which silver halochloride layers areformed. For example, dislocation lines can be provided only in aperipheral region of the major planes, excluding a central regionthereof, by using substrate grains having an internal high-silver iodidestructure with a displacement in a side direction of the tabularsubstrate grains. On the other hand, dislocation lines can be providedonly in a central region of the major planes, excluding a peripheralregion thereof, by using substrate grains having an external high-silverchloride structure with a displacement in a side direction of thetabular substrate grains. Furthermore, a silver halochloride can bedeposited only on a limited area by using a site director of epitaxialgrowth of the silver halochloride, such as an iodide; therebydislocation lines can be provided at the limited area. The temperatureat which a silver halochloride is deposited is preferably from 30° C. to70° C., and more preferably from 30° C. to 50° C. After deposition ofthe silver halochloride, halogen conversion can be performed prior to orduring the growth of shells.

The location of the internal silver halochloride layer to be formedalmost parallel to major planes preferably exists in a direction fromthe center of the width to both sides of the tabular grain; and in aregion of 5 mol % or more, but less than 100 mol %; more preferably 20mol % or more, but less than 95 mol %; and particularly preferably 50mol % or more, but less than 90 mol %, in terms of the silver amount ofthe entire grain.

The silver iodide content of the shells is preferably from 0 to 30 mol%, and more preferably from 0 to 20 mol %. The temperature and the pAgat which shells are formed are not limited in particular, but apreferable temperature is from 30° C. to 80° C. The most preferabletemperature is from 35° C. to 70° C. A preferable pAg is from 6.5 to11.5. Sometimes, the above described silver halide solvents arepreferably used, and the most preferable silver halide solvent is athiocyanate salt. Sometimes, the internal silver halochloride layerssubjected to halogen conversion cannot be identified in final grains bythe above-mentioned analytical methods, depending on the conditions,such as the degree of halogen conversion. However, dislocation lines areclearly observed.

Dislocation lines may be provided by suitably combining a method ofproviding dislocation lines at any location on major planes of thetabular grains and a method of providing dislocation lines at anylocation on the above-mentioned peripheral region of the tabular grains.

Silver halides in silver emulsions that may used in combination with thesilver halide emulsion of the present invention include silver bromide,silver iodobromide, silver iodochlorobromide, and silver chlorobromide.Preferable silver halides are silver iodobromide having a silver iodidecontent of not more than 30 mol %, or silver iodochlorobromide.

Tabular grains used in the present invention can be easily prepared bymethods described, for example, by Cleve in Photoqraphic Theory andPractice (1930), page 131; by Gutoff in Photographic Science andEngineering, Vol. 14, pages 248 to 257 (1970); and in U.S. Pat. Nos.4,434,226, 4,414,310, 4,433,048, and 4,439,520, and British Patent No.2,112,157.

Generally, a silver halide emulsion is chemically sensitized. As forchemical sensitization, for example, a method described in DieGrundlagen der Photographischen Prozesse mit Silberhalogeniden, editedby H. Frieser, Akademische Verlagsgesellschaft, pages 675 to 734 (1986),can be used.

That is, sulfur sensitization, wherein sulfur-containing compoundscapable of reacting with an active gelatin and a silver, such asthiosulfates, thioureas, mercapto compounds, and rhodanines, are used;reduction sensitization, wherein reducing substances, such as stannoussalts, amines, hydrazine derivatives, formamidine sulfinic acid, andsilane compounds, are used; noble metal sensitization, wherein noblemetal compounds, such as gold complex salts, and complex salts of othermetals of the VIII group in the periodic table (Pt, Ir, Pd, etc.), areused; and selenium sensitization, wherein selenium compounds, such asselenoureas, selenoketones, and selenides, are used, can be used aloneor in combination.

In the photographic emulsion used in the present invention, variouscompounds can be contained in order to prevent fogging during theprocess for producing the photographic material, during the storage ofthe photographic material, or during the photographic processing, or inorder to stabilize the photographic performance. That is, many compoundsknown as antifogging agents or stabilizers can be used, such as azoles,for example benzothiazolium salts, nitroimidazoles, triazoles,benzotriazoles, and benzimidazoles (particularly nitro- orhalo-substituted compound); heterocyclic mercapto compounds, for examplemercaptothiazoles, mercaptobenzothiazoles, mercaptobenzimidazoles,mercaptothiadiazoles, mercaptotetrazoles (particularly1-phenyl-5-mercaptotetrazole), and mercaptopyrimidines; the aboveheterocyclic mercapto compounds having a water-soluble group, such as acarboxyl group and a sulfone group; thioketo compounds, for exampleoxadolinethion; azaindenes, for example tetraazaindenes (particularly4-hydroxy-substituted (1,3,3a,7)tetraazaindenes); benzenethiosulfonicacids; and benzenesulfinic acids.

The addition time of these antifoggants or stabilizers is usually afterchemical sensitization, but it can be preferably selected from a periodof the middle or not later than the start of a chemical ripening. Thatis to say, in a silver halide emulsion grains formation process, theymay be added while a silver salt solution is added, or at any time offrom the addition of the silver salt solution to the start of a chemicalripening, or in the middle of a chemical ripening (i.e., during achemical ripening, preferably within a time period of from the start to50%, and more preferably 20% of the entire chemical ripening).

It is difficult to unitarily specify an addition amount of theabove-described compounds to be used in the present invention byaddition method or amount of silver halide, but a preferable amount isfrom 10⁻⁷ mol to 10⁻² mol, and more preferable amount is from 10⁻⁵ to10⁻² mol, per 1 mol of silver halide, respectively.

As a preservative (i.e., a binder or a protective colloid) for aphotographic emulsion of the present invention, gelatin is useful, andother hydrophilic colloids may be also used.

For example, proteins, such as a gelatin derivative, a graft polymer ofgelatin with other polymer, albumin, and casein; cellulose derivatives,such as hydroxyethyl cellulose, carboxymethylcellulose, and cellulosesulfate ester; saccharide derivatives, such as sodium alginate andstarch derivatives; and various synthetic hydrophilic polymers includinghomopolymers and copolymers, such as a polyvinyl alcohol, a polyvinylalcohol partial acetal, a poly-N-vinyl pyrrolidone, a polyacrylic acid,a polymethacrylic acid, a polyacrylamide, a polyvinyl imidazole, and apolyvinyl pyrazole, can be mentioned.

As a gelatin, in addition to lime-processed gelatin, an acid-processedgelatin and an enzyme-processed gelatin, as described in Bull. Soc. Sci.Photo. Japan. No. 16, p. 30 (1966), can be used, and a hydrolysate or anenzymolyte of gelatin can be used as well. As a gelatin derivative, oneobtained by reacting gelatin with various compounds, for example an acidhalide, an acid anhydride, isocyanates, a bromoacetic acid, alkanesultones, vinyl sulfonamides, maleic imide compounds,polyalkyleneoxides, and epoxy compounds, can be used.

As a dispersion medium used in the present invention, specific examplesare described in paragraph IX of Research Disclosure, Volume 176, No.17643 (December 1978).

The photographic emulsion used in the present invention is spectrallysensitized with methine dyes or the like in view of preferableexhibition of the effect of the present invention. The dyes that will beused include cyanine dyes, merocyanine dyes, composite cyanine dyes,composite merocyanine dyes, halopolar cyanine dyes, hemicyanine dyes,styrylcyanine dyes, and hemioxonol dyes. Particularly useful dyes arecyanine dyes. In these dyes, any nucleus that is generally used incyanine dyes as a basic heterocyclic nucleus can be used. That is, apyrroline nucleus, an oxazoline nucleus, a thiazoline nucleus, a pyrrolenucleus, an oxazole nucleus, a thiazole nucleus, a selenazole nucleus,an imidazole nucleus, a tetrazole nucleus, and a pyridine nucleus;nucleuses formed by fusing an cycloaliphatic hydrocarbon ring to thesenucleuses; and nucleuses formed by fusing an aromatic hydrocarbon ringto these nucleuses, i.e., an indolenine nucleus, a benzoindoleninenucleus, an indole nucleus, a benzoxazole nucleus, a naphthooxazolenucleus, a benzothiazole nucleus, a naphthothiazole nucleus, abenzoselenazole nucleus, a benzoimidazole nucleus, and a quinolinenucleus, can be applied. These nucleuses may have a substituent on thecarbon atom.

Preferable silver halide to be contained in the photographic emulsionlayer of the photosensitive material utilized in the present inventionis silver iodobromide, silver iodochloride, and silveriodochlorobromide, containing about 30 mol % or less silver iodide. Aparticularly preferable silver halide is silver iodobromide and silveriodochlorobromide, containing about 2 to about 10 mol % silver iodide.

The silver halide grains in the photographic emulsion may have a regularcrystal form, such as a cubic shape, an octahedral shape, and atetradecahedral shape, or a irregular crystal shape, such as sphericalshape or a tabular shape, or they may have a crystal defect, such astwin planes, or they may have a composite crystal form.

The silver halide grains may be fine grains having a diameter of about0.2 μm or less, or large-size grains with the diameter of the projectedarea being down to about 10 μm. As the silver halide emulsion, apolydisperse emulsion or a monodisperse emulsion can be used.

The silver halide photographic emulsions that can be used in the presentinvention may be prepared suitably by known means, for example, by themethods described in I. Emulsion Preparation and Types, in ResearchDisclosure (RD) No. 17643 (December 1978), pp. 22-23, and ibid. No.18716 (November 1979), p. 648, and ibid. No. 307105 (November, 1989),pp. 863-865; the methods described in P. Glafkides, Chimie et PhisiguePhotographigue, Paul Montel (1967), in G. F. Duffin, PhotographicEmulsion Chemistry, Focal Press (1966), and in V. L. Zelikman et al.,Making and Coating of Photographic Emulsion, Focal Press (1964).

A monodisperse emulsion, such as described in U.S. Pat. Nos. 3,574,628and 3,655,394, and in British Patent No. 1,413,748, is also preferable.

The above-described emulsion may be any of a surface latent image-typeemulsion, wherein a latent image is mainly formed on the grain surface;an internal latent image-type emulsion, wherein a latent image is formedinside the grain; and another type of emulsion, wherein a latent imageis formed both on the grain surface and inside the grain; but in anycase the above-described emulsion must be a negative-working emulsion.The internal latent image-type emulsion may be a core/shell-typeemulsion, as described in JP-A No. 264740/1988. A method of preparingthe core/shell-type, internal latent image-type emulsion is described inJP-A No. 133542/1984. The thickness of shells of the core/shell grainsis different due to such conditions as the development process, butpreferably it is from 3 nm to 40 nm, and most preferably from 5 to 20nm.

Silver halide grains whose surface was previously fogged, as describedin U.S. Pat. No. 4,082,553; silver halide grains whose internal portionwas previously fogged, as described in U.S. Pat. No. 4,626,498 and JP-ANo. 214852/1984, or a colloidal silver, may be preferably added to alight-sensitive silver halide emulsion layer and/or a substantiallynon-light-sensitive hydrophilic colloid layer. The silver halide grainswhose inside or surface was previously fogged means silver halide grainsthat are developable uniformly (non-image wise) without a distinction ofan unexposed part and an exposed part of the photosensitive material. Amethod of preparing silver halide grains whose inside or surface ispreviously fogged is described in U.S. Pat. No. 4,626,498 and JP-A No.214852/1984.

Silver halides that form internal nuclei of the core/shell-type silverhalide grains whose inside is previously fogged may be those having thesame halogen composition or those having different halogen compositions.As a silver halide whose grain inside or surface is previously fogged,any of silver chloride, silver chlorobromide, silver iodobromide, andsilver chloroiodobromide can be used. Sizes of these previously foggedsilver halide grains are not limited in particular, but an average grainsize thereof is preferably from 0.01 μm to 0.75 μm, and most preferablyfrom 0.05 μm to 0.6 μm. Further, a grain shape is not limited inparticular, and grains may be regular in shape. Moreover, theseemulsions may be a poly-dispersion emulsion, but a mono-dispersionemulsion (at least 95% of silver halide grains in weight or number havegrain diameters within ±40% of the average grain diameter) is preferred.

In the present invention, it is preferable to use a light-insensitivefine-grain silver halide. A light-insensitive fine-grain silver halidemeans silver halide fine particles that are not sensitive to light at animage-wise exposure to light for obtaining a dye image, and that are notsubstantially developable in a developing process. Preferably thesesilver halide grains are not previously fogged.

These fine-grain silver halides are those having a silver bromidecontent of from 0 mol % to 100 mol %; they may optimally contain silverchloride and/or silver iodide. Preferably they contain 0.5 mol % to 10mol % of silver iodide.

The average grain size (the average diameter of a circle having the samearea as the projected area of the grains) of fine-grain silver halidesis preferably from 0.01 μm to 0.5 μm, and more preferably from 0.02 μmto 2 μm.

The coating silver amount of the photosensitive material according tothe present invention is preferably not more than 6.0 g/m², and mostpreferably not more than 4.5 g/m².

Silver halide emulsions that are used in the present invention areusually subjected to physical ripening, chemical ripening, and spectralsensitization. Additives that are used in such steps are described inResearch Disclosures RD No. 17643, RD No. 18716, and RD No. 307105, andthey are summarized in the following table.

    __________________________________________________________________________                   RD 17643 RD 18716    RD 307105    Additive       (December 1978)                            (November 1979)                                        (November 1989)    __________________________________________________________________________    1 Chemical sensitizer                   p. 23    p. 648 (right column)                                        p. 866    2 Sensitivity-enhancing agent                   --       p. 648 (right column)                                        --    3 Spectral sensitizers and                   pp. 23-24                            pp. 648- (right column)                                        pp. 866-868      Supersensitizers      649 (right column)    4 Brightening agents                   p. 24    p. 647 (right column)                                        p. 868    5 Antifogging agents and                   pp. 24-25                            p. 649 (right column)                                        pp. 868-870      Stabilizers    6 Light absorbers, Filter                   pp. 25-26                            pg. 649- (right column)                                        p. 873      dyes, and UV Absorbers                            650 (left column)    7 Stain-preventing agent                   p. 25 (right                            p. 650 (left to right                                        p. 872                   column)  column)    8 Image dye stabilizers                   p. 25    p. 650 (left column)                                        p. 872    9 Hardeners    p. 26    p. 651 (left column)                                        pp. 874-875    10      Binders      p. 26    p. 651 (left column)                                        pp. 873-874    11      Plasticizers and Lubricants                   p. 27    p. 650 (right column)                                        p. 876    12      Coating aids and                   pp. 26-27                            p. 650 (right column)                                        pp. 875-876      Surface-active agents    13      Antistatic agents                   p. 27    p. 650 (right column)                                        pp. 876-877    14      Matting agent                   --       --          pp. 878-879    __________________________________________________________________________

Other techniques and inorganic and organic materials that can be used inthe color photosensitive material of the present invention, aredescribed in the below points of Published European Patent Application(EP-A) No. 436,938A2 and in the below-referred publications.

    ______________________________________    1.   Layer Constitution                         p 146 line 34 to p 147 line 25    2.   Yellow coupler  p 137 line 35 to p 146 line 33,                         p 149 lines 21 to 23    3.   Magenta coupler p 149 lines 24 to 28; EP-A No.                         421,453A2, p 3 line 28 to p 40                         line 2    4.   Cyan coupler    p 149 lines 29 to 33; EP-A No.                         432,804A2, p 3 line 28 to p 40                         line 2    5.   Polymer coupler p 149 lines 34 to 38; EP-A No.                         435,334A2, p 113 line 39 to                         p 123 line 37    6.   Colored coupler p 53 line 42 to p 137 line 34,                         p 149 lines 39 to 45    7.   Other functional                         p 7 line 1 to p 53 line 41, p 149         coupler         line 46 to p 150 line 3; EP-A                         No. 435,334A2, p 3 line 1 to                         p 29 line 50    8.   Antiseptic and  p 150 lines 25 to 28         mildewproofing agent    9.   Formalin scavenger                         p 149 lines 15 to 17    10.  Other additives p 153 lines 38 to 47; EP-A No.                         421,453Al, p 75 line 21 to p 84                         line 56, p 27 line 40 to p 37                         line 40    11.  Dispersion method                         p 150 lines 4 to 24    12.  Support         p 150 lines 32 to 34    13.  Thickness and   p 150 lines 35 to 49         physical properties         of membrane    14.  Color development                         p 150 line 50 to p 15l line 47         process    15.  Desilvering process                         p 151 line 48 to p 152 line 53    16.  Automatic processor                         p 152 line 54 to p 153 line 2    17.  Water washing and                         p 153 lines 3 to 37         stabilizing process    ______________________________________

According to the present invention, a silver halide photosensitivematerial having high sensitivity and low fog can be obtained.

The present invention will be described by way of its examples, below,but the invention is not limited to them.

EXAMPLE 1 (1) Preparation of Emulsions

(Em-1)

A silver iodobromide emulsion containing twin grains (a core/shellratio=1/2; iodide content of the shell, 2 mol %) having a meansphere-equivalent diameter of 1.2 μm was prepared by a controlled doublejet method in an aqueous gelatin solution, using double twin grains ofsilver iodobromide having an average iodide content of 20 mol % and amean sphere-equivalent diameter of 0.8 μm as seed grains.

After this grain formation, the emulsion was subjected to an ordinarydesalting and washing steps, and then it was redispersed under theconditions of 40° C. pAg 8.9, and pH 6.3. Further, a gold andsulfur-sensitized emulsion was prepared using sodium thiosulfate andchloroauric acid. The thus obtained emulsion was named Em-1.

(Em-2)

Em-2 was prepared in the same manner as Em-1 was, except for adding3×10⁻⁵ mol/mol Ag of the thiosulfonic acid compound, as illustratedbelow, at the step of one minute before the start of shell formation inEm-1, and adding 1×10⁻⁵ mol/mol Ag of dimethylamine borane as areduction sensitizer at the step of one minute after the start of shellformation.

Thiosulfonic acid compound C₂ H₂ SO₂ SNa

(Em-3)

Em-3 was prepared in the same manner as Em-2, except that after thesteps of a desalting, a washing, and a redispersion in the preparationof Em-2, 5×10⁻⁵ mol per mol of Ag of the compound (A-4) according to thepresent invention was added to Em-2, and then the emulsion was subjectedto the gold and sulfur sensitization.

An emulsion layer and a protective layer were coated on an undercoatedtriacetylcellulose support in the coated amount shown in Table 2, toprepare Samples 1001 to 1003 containing Em-1 to Em-3, respectively.

                  TABLE 2    ______________________________________    Conditions of Emulsion Coating    ______________________________________    (1) Emulsion layer    •          Emulsion          Emulsion Em1 to Em3                         (Silver 2.1 × 10.sup.-2                                       mol/m.sup.2)    •          Coupler        (1.5 × 10.sup.-3                                       mol/m.sup.2)     ##STR8##    •          Tricresyl phosphate                         (1.10         g/m.sup.2)    •          Gelatin        (2.30         g/m.sup.2)    (2) Protective layer    •          2,4-dichlorotriazine-6-                         (0.08         g/m.sup.2)          hydroxy-s-triazine          sodium salt    •          Gelatin        (1.80         g/m.sup.2)    ______________________________________

Each of these samples was exposed to light at color temperature 4,800°K. through a continuous wedge for 1/100 sec. for sensitometry anddeveloped according to the following color-developing process. Thedeveloping process herein used was performed at 38° C. under theconditions described below.

    __________________________________________________________________________    (Processing process)    Processing step             Time   Temperature                           Replenisher*                                    Tank Volume    __________________________________________________________________________    Color developing             2 min 45 sec                    38° C.                           33 ml    20 liter    Bleaching             6 min 30 sec                    38° C.                           25 ml    40 liter    Water washing             2 min 10 sec                    24° C.                           1200 ml  20 liter    Fixing   4 min 20 sec                    38° C.                           25 ml    30 liter    Water washing             1 min 05 sec                    24° C.                           Counter-current                                    10 liter    (1)                    piping mode from                           (2) to (1)    Water washing             1 min 00 sec                    24° C.                           1200 ml  10 liter    (2)    Stabilizing (3)             1 min 05 sec                    38° C.                           25 ml    10 liter    Drying   4 min 20 sec                    55° C.    __________________________________________________________________________     Note: *Replenisher amount per one meter length of 35 mm width.

The composition of each processing solution is shown below.

    ______________________________________                      Mother   Replenisher                      Solution (g)                               (g)    ______________________________________    (Color-developer)    Diethylenetriaminepentaacetic acid                        1.0        1.1    1-hydroxyethylidene-1,1-                        3.0        3.2    diphosphonic acid    Sodium sulfite      4.0        4.4    Potassium carbonate 30.0       37.0    Potassium bromide   1.4        0.7    Potassium iodide    1.5 mg     --    Hydroxylamine sulfate                        2.4        2.8    4-[N-Ethyl-N-β-hydroxyethylamino]-                        4.5        5.5    2-methylaniline sulfate    Water to make       1.0 liter  1.0 liter    pH                  10.05      10.10    (Bleaching solution)    Iron (III) sodium ethylenediamine-                        100.0      120.0    tetraacetate trihydrate    Disodium ethylenediamine-                        10.0       11.0    tetraacetate    Ammonium bromide    140.0      160.0    Ammonium nitrate    30.0       35.0    Aqueous ammonia (27%)                        6.5 ml     4.0 ml    Water to make       1.0 liter  1.0 liter    pH                  6.0        5.7    (Fixing solution)    Sodium ethylenediaminetetraacetate                        0.5        0.7    Sodium sulfite      7.0        8.0    Sodium bisulfite    5.0        5.5    Aqueous ammonium thiosulfite                        170.0 ml   200.0 ml    solution (70%)    Water to make       1.0 liter  1.0 liter    pH                  6.7        6.6    (Stabilizing solution)    Formalin (37%)      2.0 ml     3.0 ml    Polyoxyethylene-p-monononylphenyl                        0.3        0.45    ether (average polymerization    degree: 10)    Disodium ethylenediaminetetraacetate                        0.05       0.08    Water to make       1.0 liter  1.0 liter    pH                  5.8-8.0    5.8-8.0    ______________________________________

The optical density of each processed sample was measured by using agreen filter.

The sensitivity was shown as a relative value in logarithm of exposurethat gives an optical density of 0.2 higher than fog.

The thus obtained results are shown in Table 3.

                                      TABLE 3    __________________________________________________________________________        Reduction        sensitizer                Radical  Thiosulfonic        (Dimethylamine                scavenger                         acid        borane) (Compound A-4)                         (C.sub.2 H.sub.5 SO.sub.2 SNa)    Sample        (mol/mol Ag)                (mol/mol Ag)                         (mol/mol Ag)                                 Sensitivity                                       Fog                                          Remarks    __________________________________________________________________________    1001        --      --       --      100   0.20                                          Comparative Example    1002        3 × 10.sup.-5                --       1 × 10.sup.-5                                 132   0.25                                          Comparative Example    1003        3 × 10.sup.-5                5 × 10.sup.-4                         1 × 10.sup.-5                                 157   0.18                                          This invention    __________________________________________________________________________

Higher sensitivity is obtained by the addition of a combination ofthiosulfonic acid and dimethylamine borane as a reduction sensitizer(JP-A No. 191938/1990). Much higher sensitivity is obtained by furtheradding thereto a compound of the present invention. Moreover, at thistime, the degree of fog formed in the emulsion of the present inventionis the same level as those of emulsions prior to reductionsensitization. Therefore it is found that an emulsion having low fog andhigh sensitivity is obtained by the present invention.

EXAMPLE 2 (1) Preparation of Emulsions

(Em-11)

While an aqueous solution obtained by dissolving 6 g of potassiumbromide and 30 g of inactive gelatin having an average molecular weightof 15,000 to 3.7 liters of distilled water was agitated, a 14% aqueouspotassium bromide solution and a 20% aqueous silver nitrate solutionwere added to the above aqueous solution by a double jet method atconstant flow rates, over one minute, under the conditions of 55° C. anda pBr of 1.0 (in this addition, 2.4% of a total silver amount wasconsumed).

Then, an aqueous gelatin solution (17%, 300 cc) was added to theresultant mixture, and the solution was agitated at 55° C. Thereafter, a20% aqueous silver nitrate solution was added to the mixture at aconstant flow rate until the pBr reached 1.4 (in this addition, 5.0% ofthe total silver amount was consumed). At this time, thiourea dioxidewas added to a reaction vessel, in an amount of 1.2×10⁻⁵ mol per 1 molof silver. A 20% aqueous potassium iodobromide solution (KBr_(1-x) I_(x):x=0.04) and a 33% aqueous silver nitrate solution were further added tothe resultant mixture by the double jet method, over 43 minutes (in thisaddition, 50% of the total silver amount was consumed). At this time, anaqueous solution containing 8.3 g of potassium iodide was added to theresultant mixture. After that, 14.5 ml of a 0.001 weight % aqueous K₃IrCl₆ solution was added, and then a 20% aqueous potassium bromidesolution and a 33% aqueous silver nitrate solution were added to theresultant mixture by the double jet method, over 39 minutes (in thisaddition, 42.6% of the total silver amount was consumed; thethiosulfonic acid compound as described in Example 1 in an amount of1.2×10⁻⁴ mol per 1 mol of Ag was added at 10 minutes after the start ofthis final shell formation). The amount of silver nitrate used for thisemulsion was 425 g. Then, after a desalting according to an ordinaryflocculation, the emulsion was adjusted to a pAg of 8.2 and a pH of 5.8°at 40° C. A tabular silver iodobromide emulsion having an average aspectratio of 6.5, a variation coefficient of 18%, and a sphere-equivalentdiameter of 0.8 μm, was prepared. From observation using a transmissionelectron microscope with a voltage of 200 kv at a liquid nitrogentemperature, it was identified that an average 50 or more of dislocationlines per 1 grain existed in the vicinity of the outer surface oftabular grains.

To the thus obtained emulsion, were added 4×10⁻⁴ mol/mol Ag of thesensitizing dye A, 2×10⁻⁵ mol/mol Ag of the sensitizing dye B, and6×10⁻⁴ mol/mol Ag of the sensitizing dye C, each of which is shown inTable 4, and then this emulsion was optimally gold-selenium-sulfursensitized with sodium thiosulfate and chloroauric acid,N,N-dimethylselenourea and potassium thiocyanate, whereby Em-11 wasprepared.

                  TABLE 4    ______________________________________    Sensitizing dye A     ##STR9##    Sensitizing dye B     ##STR10##    Sensitizing dye C     ##STR11##    ______________________________________

(Em-12)

In the preparation of Em-11, 3.3×10⁻⁴ mol/mol Ag of Compound A-4according to the present invention was added at 11 minutes after thestart of the final shell formation.

(Em-13)

In the preparation of Em-11, 3.3×10⁻⁴ mol/mol Ag of Compound A-4according to the present invention was added just before the waterwashing.

(Em-14)

In the preparation of Em-11, 3.3×10⁻⁴ mol/mol Ag of Compound A-4according to the present invention was added before the addition ofsensitizing dyes.

(Em-15)

In the preparation of Em-11, 3.3×10⁻⁴ mol/mol Ag of Compound A-4according to the present invention was added after the completion ofchemical sensitization.

(Em-16)

In the preparation of Em-11, 3.3×10⁻⁴ mol/mol Ag of Compound A-3according to the present invention was added before the addition of thesensitizing dyes.

(Em-17)

In the preparation of Em-11, 3.3×10⁻⁴ mol/mol Ag of Compound A-1according to the present invention was added before the addition of thesensitizing dye.

(Em-18)

In the preparation of Em-11, 3.3×10⁻⁵ mol/mol Ag of Compound A-1according to the present invention was added before the addition of thesensitizing dyes.

(Em-19)

In the preparation of Em-11, 3.3×10⁻³ mol/mol Ag of Compound A-1according to the present invention was added before the addition of thesensitizing dyes.

An emulsion layer and a protective layer were coated on an undercoatedtriacetylcellulose support in the same manner as in Example 1, toprepare samples 1011 to 1019 containing Em-11 to Em-19, respectively.These samples 1011 to 1019 were exposed to light and developed in thesame manner as in Example 1.

The thus obtained results are shown in Table 5.

                                      TABLE 5    __________________________________________________________________________    Reduction    sensitizer    (Thiourea   Thiosulfonic                        Radical scavenger    Sample        dioxide)                acid          Added amount     Sensi-    No. (mol/mol Ag)                (mol/mol Ag)                        Compound                              (mol/mol Ag)                                      Added timing                                               tivity                                                   Fog                                                      Remarks    __________________________________________________________________________    1011        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        --    --      --       100 0.28                                                      Comparative                                                      Example    1012        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        A-4   3.3 × 10.sup.-4                                      at 11 min after                                               120 0.28                                                      This                                      start of final  Invention                                      shell formation    1013        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        A-4   3.3 × 10.sup.-4                                      just before                                               123 0.28                                                      This                                      water washing   Invention    1014        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        A-4   3.3 × 10.sup.-4                                      before addition                                               125 0.26                                                      This                                      of sensitizing dyes                                                      Invention    1015        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        A-4   3.3 × 10.sup.-4                                      after completion                                               100 0.27                                                      Comparative                                      of chemical     Example                                      sensitization    1016        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        A-3   3.3 × 10.sup.-4                                      before addition                                               130 0.22                                                      This                                      of sensitizing dyes                                                      Invention    1017        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        A-1   3.3 × 10.sup.-4                                      before addition                                               125 0.26                                                      This                                      of sensitizing dyes                                                      Invention    1018        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        A-1   3.3 × 10.sup.-5                                      before addition                                               115 0.28                                                      This                                      of sensitizing dyes                                                      Invention    1019        1.2 × 10.sup.-5                1.2 × 10.sup.-4                        A-1   3.3 × 10.sup.-3                                      before addition                                               120 0.28                                                      This                                      of sensitizing dyes                                                      Invention    __________________________________________________________________________

As is apparent from Table 5, samples 1012 to 1014 and 1016 to 1019 ofthe present invention each provide a considerable enhancement ofsensitivity without increasing fog formation, in comparison with Sample1011, which does not contain any compound according to the presentinvention. On the other hand, no increase in sensitivity was observedwith respect to sample 1015, wherein a compound according to the presentinvention was added after the completion of chemical sensitization.

EXAMPLE 3

(Sample 101)

A multilayer color photosensitive material, sample 101, was prepared bymulti-coating respective layers having compositions shown below onundercoated triacetate cellulose film support. (Composition ofphotosensitive layer)

Coating amounts for silver halide and colloidal silver are representedby g/m² in terms of silver; coating amounts for coupler, additive, andgelatin are represented by g/m², and coating amounts for sensitizing dyeare shown in mol per mol of silver halide of the same layer. Symbolsrepresenting additives have the meanings shown below, provided that foradditives having plural functions one function is described as arepresentative of the functions.

    ______________________________________    UV; Ultraviolet-rays absorber    Solv; High-boiling organic solvent    ExF; Dye    ExS; Sensitizing dye    ExC; Cyan coupler    ExM; Magenta coupler    ExY; Yellow coupler    Cpd; Additive    First Layer (Halation-preventing Layer)    Black colloidal silver    0.15    Gelatin                   2.33    UV-1                      3.0 × 10.sup.-2    UV-2                      6.0 × 10.sup.-2    UV-3                      7.0 × 10.sup.-2    ExF-1                     1.0 × 10.sup.-2    ExF-2                     4.0 × 10.sup.-2    ExF-3                     5.0 × 10.sup.-3    ExM-3                     0.11    Cpd-5                     1.0 × 10.sup.-3    Solv-1                    0.16    Solv-2                    0.10    Second Layer (Low Sensitivity Red-sensitive    Emulsion Layer)    Silver iodobromide    emulsion A Silver coating amount                              0.35    Silver iodobromide    emulsion B Silver coating amount                              0.18    Gelatin                   0.77    ExS-1                     6.5 × 10.sup.-4    ExS-2                     3.6 × 10.sup.-4    ExS-5                     6.2 × 10.sup.-4    ExS-7                     4.1 × 10.sup.-6    ExC-1                     9.0 × 10.sup.-2    ExC-2                     5.0 × 10.sup.-3    ExC-3                     4.0 × 10.sup.-2    ExC-5                     8.0 × 10.sup.-2    ExC-6                     2.0 × 10.sup.-2    ExC-9                     2.5 × 10.sup.-2    Cpd-1                     2.2 × 10.sup.-2    Third Layer (Medium Sensitivity Red-sensitive    Emulsion Layer)    Silver iodobromide    emulsion C Silver coating amount                              0.55    Gelatin                   1.46    ExS-1                     4.3 × 10.sup.-4    ExS-2                     2.4 × 10.sup.-4    ExS-5                     4.1 × 10.sup.-4    ExS-7                     4.3 × 10.sup.-6    ExC-1                     0.19    ExC-2                     1.0 × 10.sup.-2    ExC-3                     1.0 × 10.sup.-2    ExC-4                     1.6 × 10.sup.-2    ExC-5                     0.19    ExC-6                     2.0 × 10.sup.-2    ExC-7                     2.5 × 10.sup.-2    ExC-9                     3.0 × 10.sup.-2    Cpd-4                     1.5 × 10.sup.-2    Fourth Layer (High Sensitivity Red-sensitive    Emulsion Layer)    Silver iodobromide    emulsion D Silver coating amount                              1.05    Gelatin                   1.38    ExS-1                     3.6 × 10.sup.-4    ExS-2                     2.0 × 10.sup.-4    ExS-5                     3.4 × 10.sup.-4    ExS-7                     1.4 × 10.sup.-5    ExC-1                     2.0 × 10.sup.-2    ExC-3                     2.0 × 10.sup.-2    ExC-4                     9.0 × 10.sup.-2    ExC-5                     5.0 × 10.sup.-2    ExC-8                     1.0 × 10.sup.-2    ExC-9                     1.0 × 10.sup.-2    Cpd-4                     1.0 × 10.sup.-3    Solv-1                    0.70    Solv-2                    0.15    Fifthe Layer (Intermediate Layer)    Gelatin                   0.62    Cpd-1                     0.13    Poly(ethyl acrylate) latex                              8.0 × 10.sup.-2    Solv-1                    8.0 × 10.sup.-2    Sixth Layer (Low Sensitivity Green-sensitive    Emulsion Layer)    Silver iodobromide    emulsion B Silver coating amount                              0.10    Silver iodobromide    emulsion A Silver coating amount                              0.28    Gelatin                   0.31    ExS-4                     12.8 × 10.sup.-4    ExS-5                     2.1 × 10.sup.-4    ExS-8                     1.2 × 10.sup.-4    ExM-1                     0.12    ExM-7                     2.1 × 10.sup.-2    Solv-1                    0.09    Solv-3                    7.0 × 10.sup.-3    Seventh Layer (Medium Sensitivity Green-    sensitive Emulsion Layer)    Silver iodobromide    emulsion C Silver coating amount                              0.37    Gelatin                   0.54    ExS-4                     8.5 × 10.sup.-4    ExS-5                     1.4 × 10.sup.-4    ExS-8                     8.3 × 10.sup.-5    ExM-1                     0.27    ExM-7                     7.2 × 10.sup.-2    ExY-1                     5.4 × 10.sup.-2    Solv-1                    0.23    Solv-3                    1.8 × 10.sup.-2    Eighth Layer (High Sensitivity Green-sensitive    Emulsion Layer)    Silver iodobromide    emulsion D Silver coating amount                              0.53    Gelatin                   0.61    ExS-4                     7.1 × 10.sup.-4    ExS-5                     1.4 × 10.sup.-4    ExS-8                     4.6 × 10.sup.-5    ExM-2                     5.5 × 10.sup.-3    ExM-3                     1.0 × 10.sup.-2    ExM-5                     1.0 × 10.sup.-2    ExM-6                     3.0 × 10.sup.-2    ExY-1                     1.0 × 10.sup.-2    ExC-1                     4.0 × 10.sup.-3    ExC-4                     2.5 × 10.sup.-3    Cpd-6                     1.0 × 10.sup.-2    Solv-1                    0.12    Ninth Layer (Intermediate Layer)    Gelatin                   0.56    UV-4                      4.0 × 10.sup.-2    UV-5                      3.0 × 10.sup.-2    Cpd-1                     4.0 × 10.sup.-2    Poly(ethyl acrylate) latex                              5.0 × 10.sup.-2    Solv-1                    3.0 × 10.sup.-2    Tenth Layer (Donner Layer of Interlayer Effect    for Red-sensitive Layers)    Silver iodobromide    emulsion E Silver coating amount                              0.40    Silver iodobromide    emulsion F Silver coating amount                              0.20    Silver iodobromide    emulsion G Silver coating amount                              0.39    Gelatin                   0.87    ExS-3                     9.8 × 10.sup.-4    ExM-2                     0.16    ExM-4                     3.0 × 10.sup.-2    ExM-5                     5.0 × 10.sup.-2    ExY-2                     2.5 × 10.sup.-3    ExY-5                     2.0 × 10.sup.-2    Solv-1                    0.30    Solv-5                    3.0 × 10.sup.-2    Eleventh Layer (Yellow Filter Layer)    Yellow colloidal silver   4.2 × 10.sup.-2    Dye-1                     1.02 × 10.sup.-1    Gelatin                   0.84    Cpd-1                     5.0 × 10.sup.-2    Cpd-2                     5.0 × 10.sup.-2    Cpd-5                     2.0 × 10.sup.-3    Solv-1                    0.13    H-1                       0.25    Twelfth Layer (Low Sensitivity Blue-sensitive    Emulsion Layer)    Silver iodobromide    emulsion A Silver coating amount                              0.50    Silver iodobromide    emulsion H Silver coating amount                              0.40    Gelatin                   1.75    ExS-6                     9.0 × 10.sup.-4    ExY-1                     8.5 × 10.sup.-2    ExY-2                     5.5 × 10.sup.-3    ExY-3                     6.0 × 10.sup.-2    ExY-5                     1.00    ExC-1                     5.0 × 10.sup.-2    ExC-2                     8.0 × 10.sup.-2    Solv-1                    0.54    Thirteenth Layer (Intermediate Layer)    Gelatin                   0.30    ExY-1                     0.14    Solv-1                    0.14    Fourteenth Layer (High Sensitivity Blue-    sensitive Emulsion Layer)    Silver iodobromide    emulsion I Silver coating amount                              0.40    Gelatin                   0.95    ExS-6                     6.3 × 10.sup.-4    ExY-2                     1.0 × 10.sup.-2    ExY-3                     2.0 × 10.sup.-2    ExY-5                     0.18    ExC-1                     1.0 × 10.sup.-2    Solv-1                    9.0 × 10.sup.-2    Fifteenth Layer (First Protective Layer)    Fine-grain silver iodobromide    emulsion J Silver coating amount                              0.12    Gelatin                   0.63    UV-4                      0.11    UV-5                      0.18    Cpd-3                     0.10    Solv-1                    2.0 × 10.sup.-2    Poly(ethyl acrylate) latex                              9.0 × 10.sup.-2    Sixteenth Layer (Second Protective Layer)    Fine-grain silver iodobromide    emulsion J Silver coating amount                              0.36    Gelatin                   0.85    B-1 (diameter 2.0 μm)  8.0 × 10.sup.-2    B-2 (diameter 2.0 μm)  8.0 × 10.sup.-2    B-3                       2.0 × 10.sup.-2    W-5                       2.0 × 10.sup.-2    H-1                       0.18    ______________________________________

In addition to the above, the thus prepared Sample was added 1,2-benzisothiazoline-3-one (average 200 ppm to gelatin),n-butyl-p-hydroxybenzoate (average about 1,000 ppm to gelatin), and2-phenoxyethanol (average about 10,000 ppm to gelatin). Further, inorder to improve stability, processing property, pressure resistance,keeping property from mold and fungi, antistatic property, and coatingproperty, besides above-mentioned components, W-1 to W-6, B-1 to B-6,F-1 to F-10, F-13 to F-16 and iron salt, lead salt, gold salt, platinumsalt, iridium salt, rhodium salt were optionally contained in allemulsion layers.

                                      TABLE 6    __________________________________________________________________________                        Diviation                        coefficient         Average AgI    concerning                               Ratio of         content                Average grain                        grain  diameter/                                     Structure    Emulsion         (mol %)                diameter (μm)                        diameter (%)                               thickness                                     of grains    __________________________________________________________________________    A    3.0    0.28    23     4.5   Tabular grains    B    3.0    0.35    25     5.6   Tabular grains    C    8.8    0.53    22     5.5   Tabular grains    D    8.8    0.67    26     6.0   Tabular grains    E    2.5    0.28    21     4.8   Tabular grains    F    3.5    0.60    23     5.2   Tabular grains    G    3.4    0.53    25     5.8   Tabular grains    H    8.8    0.62    26     6.0   Tabular grains    I    8.8    0.75    26     6.5   Tabular grains    J    2.0    0.07    15     1.0   Uniform                                     structure,                                     fine grains    __________________________________________________________________________

In Table 6:

(1) Emulsions A to I were subjected to reduction sensitization usingthiourea dioxide and thiosulfonic acid in accordance with Examples givenin JP-A No. 191938/1990 when the grains were prepared.

(2) In the preparation of tabular grains, low-molecular weight gelatinswere used in accordance with Examples given in JP-A No. 158426/1989.

(3) Dislocation lines as described in JP-A No. 237450/1991 were observedin the tabular grains under a high-voltage electron microscope.

(4) Emulsions A to N contained iridium inside of grain by the methoddescribed, for example, in B. H. Carroll, Photographic Science andEngineering, 24, 265 (1980 ) .

Compounds added to the layers are shown below. ##STR12## (Sample 102)

In the preparation of Sample 101, 3×10⁻⁴ mol/mol Ag of Compound (A-3)according to the present invention was added in each emulsion layer.

(Sample 103)

In the preparation of Sample 101, 6×10⁻⁴ mol/mol Ag of Compound (A-3)according to the present invention was added in each emulsion layer.

(Sample 104)

In the preparation of Sample 101, 3×10⁻⁴ mol/mol Ag of Compound (A-3)according to the present invention was added in emulsions A to I,respectively, before chemical sensitization of the emulsions.

(Sample 105)

In the preparation of Sample 104, 3×10⁻⁴ mol/mol Ag of Compound (A-3)according to the present invention was added in each emulsion layer.

Each of the thus prepared Samples 101 to 105 was exposed to lightthrough a usual wedge for 1/100 sec. and developed according to thecolor-developing process in Example 1, provided that thecolor-developing time was 3 min 15 sec. Then, the magenta density ofeach processed sample was measured.

The sensitivity was shown as a relative value of magenta density inlogarithm of reciprocal of exposure that gives a density of fog+0.2 (Thesensitivity was a relative value to that for Sample 101 being 100).

The results are shown in Table 7.

                                      TABLE 7    __________________________________________________________________________         Added amount         of radical                 Adding method         scavenger A-3                 of radical    Sample         (mol/mol Ag)                 scavenger                          Sensitivity                                Fog Remarks    __________________________________________________________________________    101  --      --       100   0.12                                    Comparative                                    Example    102  3 × 10.sup.-4                 just before                          100   0.11                                    Comparative                 coating            Example    103  6 × 10.sup.-4                 just before                          100   0.10                                    Comparative                 coating            Example    104  3 × 10.sup.-4                 in emulsion                          115   0.08                                    This                 (before chemical   Invention                 sensitization)    105  3 × 10.sup.-4                 in emulsion                          118   0.08                                    This                 (before chemical   Invention                 sensitization)         +       +         6 × 10.sup.-4                 just before                 coating    __________________________________________________________________________

As is apparent from Table 7, Samples 102 and 103, to each of which wasadded a compound according to the present invention at the time ofcoating, provided almost no change of photographic properties, incomparison with Sample 101. On the other hand, Sample 104, in which thecompound according to the present invention was added to the emulsionbefore chemical sensitization of the emulsion, provided a considerableenhancement of sensitivity. Additionally, Sample 105, prepared by addingmore of the compound according to the present invention than was used inSample 104, provided greater sensitivity than that of Sample 104.

With respect to cyan density and yellow density, the same results wereobtained.

Having described our invention as related to the present embodiments, itis our intention that the invention not be limited by any of the detailsof the description, unless otherwise specified, but rather be construedbroadly within its spirit and scope as set out in the accompanyingclaims.

What we claim is:
 1. A method of manufacturing a silver halide emulsion, which comprises:subjecting a silver halide emulsion to reduction sensitization; adding to said reduction sensitized emulsion at least one radical scavenger represented by formula (A): ##STR13## wherein R_(a1) represents an alkyl group, and alkenyl group, an aryl group, a heterocyclic group, an acyl group, a sulfonyl group, a sulfinyl group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group; R_(a2) is a hydrogen atom or a group represented by R_(a1), with the proviso that when R_(a1) is an alkyl group, an alkenyl group, or an aryl group, R_(a2) is a heterocyclic group, an acyl group, a sulfonyl group, a sulfinyl group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group; and R_(a1) and R_(a2) may combine together to form a 5- to 7-membered ring; and subjecting said reduction sensitized emulsion to gold chalcogen sensitization; wherein said radical scavenger is added prior to completion of said gold chalcogen sensitization.
 2. The method of manufacturing a silver halide emulsion as claimed in claim 1, wherein the emulsion is subjected to reduction sensitization during growth of the silver halide grains of the emulsion.
 3. The method of manufacturing a silver halide emulsion as claimed in claim 1, wherein the radical scavenger is added before the beginning of chemical sensitization.
 4. The method of manufacturing a silver halide emulsion as claimed in claim 1, wherein the radical scavenger is contained in an amount of 1×10⁻⁵ to 1×10⁻² mol/mol Ag.
 5. A silver halide photosensitive material that comprises a support having thereon at least one layer containing a silver halide emulsion, said silver halide emulsion containing reduction and gold chalcogen sensitized silver halide grains and a radical scavenger represented by formula (A): ##STR14## wherein R_(a1) represents an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, an acyl group, a sulfonyl group, a sulfinyl group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group; R_(a2) is a hydrogen atom or a group represented by R_(a1), with the proviso that when R_(a1) is an alkyl group, an alkenyl group, or an aryl group, R_(a2) is a heterocyclic group, an acyl group, a sulfonyl group, a sulfinyl group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group; and R_(a1) and R_(a2) may combine together to form a 5- to 7-membered ring;wherein said radical scavenger was added to said emulsion after reduction sensitization and prior to the completion of gold chalcogen sensitization.
 6. The silver halide photosensitive material as claimed in claim 5, wherein the emulsion was subjected to reduction sensitization during growth of the silver halide grains of the emulsion.
 7. The silver halide photosensitive material as claimed in claim 5, wherein the radical scavenger is added before the beginning of chemical sensitization.
 8. The silver halide photosensitive material as claimed in claim 5, wherein the radical scavenger is contained in an amount of 1×10⁻⁵ to 1×10⁻² mol/mol Ag.
 9. The silver halide photosensitive material as claimed in claim 5, containing at least one compound selected from the compounds represented by general formula (B), (C), or (D):general formula (B) R³ --SO₂ S--M general formula (C) R³ --SO₂ S--R⁴ general formula (D) R³ --SO₂ S--L_(m) --SSO₂ --R⁵ wherein R³, R⁴, and R⁵, which are same or different, each represent an aliphatic group, an aromatic group, or a heterocyclic group; L represents a divalent group; M represents a cation; and m represents an integer of 0or
 1. 10. The silver halide photosensitive material as claimed in claim 9, containing a compound represented by the general formula (B).
 11. The silver halide photosensitive material as claimed in claim 9, wherein the compound represented by general formula (B), (C), or (D) is added during growth of the silver halide grains of the emulsion.
 12. The silver halide photosensitive material as claimed in claim 5, containing at least a color coupler.
 13. A silver halide photosensitive material, comprising at least one silver halide emulsion layer on a support, wherein the emulsion layer comprises a silver halide emulsion having (1) reduction and chemically sensitized silver halide grains and (2) a radical scavenger represented by general formula (A),wherein said radical scavenger was added to said emulsion prior to the completion of chemical sensitization: ##STR15## wherein R_(a1) represents an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, an acyl group, a sulfonyl group, a sulfinyl group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group; R_(a2) is a hydrogen atom or a group represented by R_(a1), with the proviso that when R_(a1) is an alkyl group, an alkenyl group, or an aryl group, R_(a2) is a heterocyclic group, an acyl group, a sulfonyl group, a sulfinyl group, a carbamoyl group, a sulfamoyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group; and R_(a1) and R_(a2) may combine together to form a 5- to 7-membered ring.
 14. The silver halide photosensitive material as claimed in claim 13, wherein said reduction and chemically sensitized silver halide grains in said emulsion are tabular silver halide grains having an aspect ratio of not less than 3, and having dislocation lines, in an amount of at least 60% of the total projected area of these grains.
 15. The silver halide photosensitive material as claimed in claim 13, containing at least a color coupler.
 16. The silver halide photosensitive material as claimed in claim 13, wherein the emulsion was subjected to reduction sensitization during growth of the silver halide grains of the emulsion.
 17. The silver halide photosensitive material as claimed in claim 13, wherein R_(a1) is a heterocyclic group.
 18. The silver halide photosensitive material as claimed in claim 13, wherein R_(a1) is a heterocyclic aromatic group.
 19. The silver halide photosensitive material as claimed in claim 13, wherein the radical scavenger is represented by general formula (A-I): ##STR16## wherein R'_(a2) represents at hydrogen atom, an alkyl group, an alkenyl group, or an aryl group, and Z represents a heterocyclic aromatic group.
 20. The silver halide photosensitive material as claimed in claim 13, wherein the radical scavenger is represented by general formula (A-II): ##STR17## wherein R'_(a2) represents a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group, and R_(a3) and R_(a4), which are same or different, each represent a hydrogen atom or a substituent.
 21. The silver halide photosensitive material as claimed in claim 13, wherein the radical scavenger is added before the beginning of chemical sensitization.
 22. The silver halide photosensitive material as claimed in claim 13, wherein the radical scavenger is contained in an amount of 1×10⁻⁵ to 1×10⁻² mol/mol Ag.
 23. The silver halide photosensitive material as claimed in claim 13, containing at least one compound selected from the compounds represented by general formula (B), (C), or (D):general formula (B) R³ --SO₂ S--M general formula (C) R³ --SO₂ S--R⁴ general formula (D) R³ --SO₂ S--L_(m) --SSO₂ --R⁵ wherein R³, R⁴, and R⁵, which are same or different, each represent an aliphatic group, an aromatic group, or a heterocyclic group; L represents a divalent group; M represents a cation; and m represents an integer of 0 or
 1. 24. The silver halide photosensitive material as claimed in claim 23, containing a compound represented by the general formula (B).
 25. The silver halide photosensitive material as claimed in claim 23, wherein the compound represented by general formula (B), (C), or (D) is added during growth of the silver halide grains of the emulsion. 